Parkinson's disease is a progressive neurodegenerative disorder which often results in disability. If pharmacological agents could slow the progression of disease early disability, job loss, and nursing home placement might be delayed. This clinical trial utilizing a randomized, double blind design will evaluate the efficacy of one or more pharmacological agents for slowing progression of Parkinson's disease and will determine the toxicity and tolerability of these agents. The trial will enroll patients with Parkinson's disease who recently started dopaminergic therapy, will be able to detect small treatment effects, will incorporate innovative sample follow-up methods, and will be able to distinguish neuroprotective effects from occult symptomatic benefits. This center will be one of 42 clinical centers designated to participate in this study.